The present invention is directed to products and processes for the neutralization of gaseous corrosive elements.
Many items degrade or tarnish with the passage of time. Metals corrode (tarnish) via several routes, including atmospheric corrosion, galvanic corrosion, and fungal attack. In the case of atmospheric corrosion, the tarnishing occurs by reaction with common gases in the atmosphere. These corrosive gases react with both Ferrous (Iron based) and Non-Ferrous metals. With Non-Ferrous metals (such as Silver, Tin, Copper, Brass, etc.), these gases are usually the primary cause for corrosion.
The most common corrosive gases in the atmosphere are Hydrogen Sulfide (H2S), Carbonyl Sulfide (COS), Sulfur Dioxide (SO2), Hydrogen Chloride (HCl), and Ozone (O3). Hydrogen Sulfide (H2S) is produced as affluent from pulp mills, oil refineries, heavy industry and from decaying vegetation. Carbonyl Sulfide (COS) is produced from fossil fuel combustion (such as burning coal, gasoline or petrol, oil, etc.), wood fires, and under sea fissures which cause an emanation from ocean surfaces. Sulfur Dioxide (SO2) is produced from fossil fuel combustion and from smelting operations. Hydrogen Chloride (HCl) is produced from fossil fuel combustion and reactions with salt water. Ozone (O3) is also produced as a byproduct of combusting fossil fuels.
Metals in nature always assume their most stable state, which in most cases are sulfides, chlorides, oxides, or other salts. As a result, metals begin corroding as soon as they are exposed to the environment. In addition, the most sensitive time for a metal is when it is pristine. In storage, shipment, or manufacture, metals are pristine, and are targets for corrosive gas attack. This corrosion or tarnishing is a particular problem for consumers purchasing fine silver, valuable coins, and so forth.
To address the problems of metal corrosion, U.S. Pat. No. 4,944,916 issued to Franey (xe2x80x9cthe Franey patentxe2x80x9d) discloses polymeric bags for preventing the permeation of corrosive materials. However, in some applications, polymeric bags are inconsistent with the traditional methods of packaging or display. Likewise, numerous other types of valuable products other than metals can degrade over time, including paper products such as rare comic books, or so forth. Accordingly, there is a need in the art for paper and foam core based products that inhibit corrosion.
A further problem in the current art is that many materials used in consumer and commercial applications (including construction, clothing, natural materials, manmade materials, appliances, and other products) sustain high humidity in their composition. As a result of this water content, those materials are particularly prone to microbial growths, such as mildew and mold. In many cases it is difficult, not safe, or not practical to use active mildewcides, or fungicides to combat the mold and mildew formation. Thus, there is also a need to reduce mildew and fungal growth on valuable materials, particularly those intended for long term storage.
It is an object of the present invention to provide methods and products for inhibition of material degradation.
It is a further object of the present invention to provide paper and foam core packaging in which reactive polymers have been incorporated to prevent corrosion.
It is a further object of the present invention to provide packaging that inhibits degradation of the material stored therein, and, in particular, which inhibits corrosion.
It is a further object of the present invention to provide paper and foam core packaging that incorporates reactive polymers to reduce microbial growth, such as mildew and fungus.
It is a yet a further object of the present invention to provide packaging which inhibits microbial growth, such as mildew and fungal growth, on the material stored in the package.
Further objects of the invention will become apparent in conjunction with the disclosure provided herein.
In accordance with the present invention, methods are provided for incorporating reactive polymers into paper and foam core materials. Such methods are employed to produce packaging for storage purposes that protects a product stored within the packaging from experiencing corrosive gases. Alternatively or additionally, the methods can be used to reduce or prevent the growth of undesirable mildew and/or fungus on the product.
In a further embodiment, a paper or foam core product can incorporate a reactive polymer to provide the product itself with corrosion resistant properties, and to inhibit mildew and fungal growth thereon. This can be especially advantageous, for example, in the case of valuable documents.
Thus, using the current methods, the surfaces of paper or foam core products are treated for the purpose of inhibiting degradation resulting from contact with atmospheric gases, whether the degradation of the paper and foam core products themselves, or the degradation of other items placed within those products when the paper and foam products are used as packaging. Such degradation can be in the form of corrosion and/microbial growth (particularly mildew and fungus).
Such undesirable degradation is minimized or prevented using reactive polymers which have been incorporated into or applied to the surface of the paper and foam core, as disclosed herein. By xe2x80x9creactive polymerxe2x80x9d (RP) the present invention refers to compounds wherein solid-state reactive materials are incorporated into a polymer matrix. More specifically, such reactive polymers are polymers incorporating a corrosive gas reactant material (the reactant material being any of the transition metals), the reactant material having been catalyzed to become part of the polymeric structure. Such reactive polymers were developed by ATandT Bell Laboratories (currently known as Lucent Bell Labs Technologies), and are disclosed in U.S. Pat. No. 4,944,916 issued to Franey. Similarly, they are discussed in John Franey, A New ESD Corrosion Preventive Polymer, EOS/ESD Symposium Proceedings 1991, EOS/ESD Association, Rome N.Y. (which association has a website at www. esda.org), and are discussed at www. staticintercept.com. The contents of that publication and those websites are fully incorporated herein by reference. The materials neutralize corrosive gases commonly associated with corrosion and tarnishing, preventing them from interacting with the underlying material of the protected product or from interacting with the product""s contents. Alternatively or additionally, the reactive polymers include copper, which has been known to be a passive mildewcide and fungicide when in intimate contact with an object.
In the preferred embodiment of the invention, the reactive polymers are those available from Engineered Materials, Inc. of Buffalo Grove, Ill. under the trade names Static Intercept(copyright) and Corrosion Intercept(trademark). The corrosion reactive polymers are manufactured by catalyzing copper material into polymer chains to form a homogeneous polymeric/metallic structure of low-density polyethylene (LDPE). The static version uses the structure of the corrosion polymer plus an additional catalysis of C12 into the poly-metallic structure to form a copper/metal/oxide semi-conductive media, which utilize the xe2x80x98Bucky Ballxe2x80x99 phenomena to provide paths for electron flow within the structure. The LDPE structures are formed into standard pellets and processed into various final structures, the most common of which is blown film to manufacture bags.
Once incorporated with reactive polymer, the surfaces of the packaging preferably have a chemically neutral pH (preferably in the approximate range of 7.0 to 7.5). Packages are designed so that, when closed, they have RP on the majority of the inside surfaces. In the preferred embodiment of the invention, the treated surfaces of the packaging have greater than two square centimeters of RP surface per square centimeter of surface of the product to be protected therein. Further preferably, the permeability of any package cross sectional structure is approximately or less than 0.015 g/M2 Moisture Vapor Transmission Rate.
Also in accordance with the invention, the paper based packaging materials are comprised of cellulose-based packaging materials, which are of high alpha-cellulose content and are negative to lignin side chains. When packed with the material to be protected, the unfilled interior volume of the package is preferably less than 25% of the total interior volume of the enclosure. In addition, adhesives are avoided in the packaging (and/or in the product), or adhesives are used having chemicals that do not contribute to the corrosion or other degradation of the material to be protected.